Vertical switched filter bank

ABSTRACT

A microwave or radio frequency (RF) device includes stacked printed circuit boards (PCBs) mounted on a flexible PCB having at least one ground plane and a signal terminal. Each of the stacked PCBs includes through-holes the sidewalls of which are coated with a conductive material. Microwave components are mounted on the flexible PCB within the through-holes, such that signal terminals of the components bond to signal terminals of respective through-holes. A conductive cover is mounted on the PCBs such that the cover is in electrical contact with the ground plane of the flexible PCB through the conductive material, forming shielding cavities around the components. The flexible PCB is folded such that the cover of one PCB faces the cover of the second PCB. The flexible PCB includes striplines or microstrips that carry RF or microwave signals to the signal terminals.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/557,632, filed Sep. 12, 2017, entitled “Vertical Switched FilterBank,” the entire contents of which are incorporated herein byreference.

BACKGROUND

Microwave and RF circuits can be implemented on circuit boards usingmicrowave and RF components and transmission lines. The sizes of theprinted circuit boards can be affected by large distances betweenneighboring components and transmission lines applied in order tomaintain signal isolation.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description and appended claims,taken in conjunction with the accompanying drawings. Understanding thatthese drawings depict only several embodiments in accordance with thedisclosure and are, therefore, not to be considered limiting of itsscope, the disclosure will be described with additional specificity anddetail through use of the accompanying drawings.

FIG. 1 shows a top view of a first example microwave device according toembodiments of the present disclosure.

FIG. 2 shows a cross-sectional view of the first example microwavedevice shown in FIG. 1.

FIG. 3 shows a cross-sectional view of a second example microwave deviceaccording to embodiments of the present disclosure.

FIG. 4 shows a top view of the second example microwave device shown inFIG. 3.

FIG. 5 shows a top view of a third example microwave device according toembodiments of the present disclosure.

FIG. 6 shows a top view of a fourth example microwave device 400including microstrip transmission lines, according to embodiments of thepresent disclosure.

FIGS. 7A and 7B show a side view and an expanded view of a bottomprinted circuit board of the third example microwave device shown inFIG. 5.

FIG. 8 shows a cross-sectional view of the third example microwavedevice shown in FIG. 5 in a folded configuration along axis B-B.

FIG. 9 shows an expanded view of a portion A of the third examplemicrowave device shown in FIGS. 5 and 8.

FIG. 10 shows an expanded view of a portion A of the fourth examplemicrowave device shown in FIGS. 6 and 8.

FIGS. 11 and 12 show block diagrams of an unfolded and a foldedmicrowave device including three stackable PCBs.

FIG. 13 shows a flow diagram for a process of manufacturing a microwavedevice, according to embodiments of the present disclosure.

FIG. 14 shows a flow diagram of another process of manufacturing amicrowave device, according to embodiments of the present disclosure.

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects of thepresent disclosure, as generally described herein, and illustrated inthe figures, can be arranged, substituted, combined, and designed in awide variety of different configurations, all of which are explicitlycontemplated and make part of this disclosure.

DETAILED DESCRIPTION

The present disclosure describes devices and techniques for a microwaveor radio frequency (RF) device. The device includes a printed circuitboards (PCB) mounted on a substrate having at least one ground plane anda signal terminal. The PCB includes through-holes the sidewalls of whichare coated with a conductive material. Microwave components are mountedon the substrate within the through-holes, such that signal terminals ofthe components bond to signal terminals of respective through-holes. Aconductive cover is mounted on the PCB such that the cover is inelectrical contact with the ground plane of the substrate through theconductive material, forming shielding cavities around the components.

In one or more embodiments, the substrate is a flexible PCB layerincluding striplines and/or microstrip transmission lines, and at leasttwo PCBs are bonded to the flexible PCB such that the at least two PCBsare stacked. The flexible PCB is folded such that the cover of one PCBfaces the cover of the second PCB. The striplines carry RF or microwavesignals to the signal terminals, and are shielded by at least two groundplanes in the flexible PCB.

In one aspect, this disclosure describes a microwave device. Themicrowave device includes a first substrate having a top surface, thetop surface having at least one ground terminal and at least one signalterminal of the first substrate. The microwave device further includes asecond substrate having a first surface and an opposing second surface,the second substrate disposed over the top surface of the firstsubstrate, the second substrate having a through-hole extending betweenthe first surface and the second surface. The microwave device furtherincludes a conductive material covering sidewalls of the through-hole,and covering at least a portion of the first surface and at least aportion of the second surface at rim edges of the through-hole, theconductive material on the first surface in electrical contact with theat least one ground terminal of the first substrate. The microwavedevice further includes a microwave component disposed within thethrough-hole and on the top surface of the first substrate, themicrowave component having a ground terminal in electrical contact withthe at least one ground terminal of the first substrate, and a signalterminal in electrical contact with the at least one signal terminal ofthe first substrate. The microwave device also includes a cover at leastpartially covering the through-hole, the cover including a conductivesurface in electrical contact with the conductive material covering atleast a portion of the second surface of the second substrate.

In some embodiments, the microwave device further includes at least onetransmission line coupled to the at least one signal terminal, and adielectric material in the first substrate covering at least a portionof the at least one transmission line. In some embodiments, themicrowave device includes a first ground plane and a second ground planedisposed on the first substrate, the at least one transmission linedisposed between the first ground plane and the second ground plane. Insome embodiments, the microwave device includes at least one microstriptransmission line coupled to the at least one signal terminal, the atleast one microstrip transmission line disposed over the top surface ofthe first substrate. In some embodiments, a cavity extends over the atleast one microstrip transmission line and is located below the firstsurface of the second substrate. In some embodiments, the microwavedevice also includes a ground plane disposed on the first substrate, theat least one microstrip transmission line separated from the groundplane by a dielectric material. In some embodiments, the conductivematerial covers all surfaces of the sidewalls of the through-hole.

In some embodiments, the conductive material comprises a layer ofconductive material having a mesh structure. In some embodiments, themicrowave device includes a first ground plane disposed over the topsurface of the first substrate, the first ground plane, the conductivematerial, and the cover forming a shielding enclosure for the microwavecomponent. In some embodiments, the microwave component has a thicknessbetween 0.045 inches to 0055 inches.

In another aspect, this disclosure discusses a microwave deviceincluding a first substrate having a first ground plane. The microwavedevice further includes a second substrate including a plurality ofthrough-holes having conductive sidewalls. The microwave device alsoincludes a plurality of microwave components disposed over the firstsubstrate within the respective through-holes. The microwave device alsoincludes a conductive cover disposed over the second substrate andpositioned to at least partially cover the plurality of through-holes,the cover electrically coupled to the first ground plane via theconductive sidewalls.

In some embodiments, the first substrate includes a plurality of signalterminals, each signal terminal of the plurality of signal terminalscoupled to a signal terminal of a respective microwave component of theplurality of microwave components. In some embodiments, the microwavedevice further includes a plurality of transmission lines coupled to arespective signal terminal of the plurality of microwave components, anda dielectric material disposed in the first substrate covering at leasta portion of each of the plurality of transmission lines. In someembodiments, the microwave device also includes a second ground planedisposed on the first substrate, wherein the plurality of transmissionlines is disposed between the first ground plane and the second groundplane. In some embodiments, the microwave device further includes aplurality of microstrip transmission lines coupled to a respectivesignal terminal of the plurality of microwave components, at least oneof the plurality of microstrip transmission lines disposed over a topsurface of the first substrate, the top surface of the first substratefacing the second substrate.

In some embodiments, the microwave device also includes a plurality ofcavities each extending over a respective one of the plurality ofmicrostrip transmission lines and located below a first surface of thesecond substrate. In some embodiments, the microwave device alsoincludes a ground plane disposed on the first substrate, the pluralityof microstrip transmission lines separated from the ground plane by adielectric material. In some embodiments, the plurality of microwavecomponents are configured to operate within a frequency range of 300 MHzto 300 GHz. In some embodiments, the conductive sidewalls include alayer of conductive material having a mesh shaped structure. In someembodiments, the plurality of microwave components have a thicknessbetween 0.045 inches to 0055 inches.

In another aspect, this disclosure describes a microwave device. Themicrowave device includes a flexible printed circuit board (PCB). Themicrowave device also includes a first PCB including a first pluralityof through-holes, the first PCB bonded to the flexible PCB. Themicrowave device also includes a first plurality of electricalcomponents bonded to the flexible PCB within respective first pluralityof through-holes. The microwave device also includes a first covercovering the first PCB. The microwave device further includes a secondPCB including a second plurality of through-holes, the second PCB bondedto the flexible PCB and spaced apart from the first PCB exposing a bendportion of the flexible PCB, the second PCB including a secondconductive layer covering sidewalls of the second plurality ofthrough-holes. The microwave device also includes a second plurality ofelectrical components bonded to the flexible PCB within respectivesecond plurality of through-holes. The microwave device further includesa second cover covering the second PCB and making electrical contactwith the second conductive layer, where the second PCB is stacked on thefirst PCB such that the first cover faces the second cover.

In some embodiments, the microwave device further includes a first rigidlayer disposed on a side of the flexible PCB opposing to a side on whichthe first PCB is disposed. In some embodiments, the first cover and thesecond cover comprise stainless steel. In some embodiments, themicrowave device further includes an adhesive layer disposed between thefirst cover and the second cover. In some embodiments, the first PCBincludes a first curved portion adjacent to the bend portion of theflexible PCB, and the second PCB includes a second curved portionadjacent to the bend portion of the flexible PCB. In some embodiments,the first curved portion and the second curved portion conform to acurvature of the bend portion of the flexible PCB. In some embodiments,the microwave device further includes an adhesive layer disposed betweenthe first curved portion of the first PCB and the bend portion of theflexible PCB.

In some embodiments, the flexible PCB includes at least one signalterminal coupled to at least one electrical component from the firstplurality of electrical components and the second plurality ofelectrical components, at least one transmission line coupled to the atleast one signal terminal, and a dielectric material covering at least aportion of the at least one transmission line. In some embodiments, theflexible PCB has at least one ground plane, the at least one groundplane including a first ground plane and a second ground plane, andwherein the at least one transmission line is disposed between the firstground plane and the second ground plane. In some embodiments, theflexible PCB includes at least one signal terminal coupled to at leastone electrical component from the first plurality of electricalcomponents and the second plurality of electrical components, at leastone microstrip transmission line coupled to the at least one signalterminal.

In some embodiments, the first PCB includes at least one cavityextending over at least a portion of a respective at least onemicrostrip transmission line, and includes a first conductive layercovering sidewalls of the first plurality of through-holes, wherein thefirst conductive layer covers at least a portion of sidewalls of the atleast one cavity. In some embodiments, the flexible PCB has at least oneground plane, and the first PCB includes a dielectric layer separatingthe at least one microstrip transmission line from the at least oneground plane. In some embodiments, the dielectric layer has a dielectricconstant between 1.5 and 3.5. In some embodiments, the dielectric layerhas a dielectric loss tangent value between 0.001 and 0.002. In someembodiments, a thermal expansion coefficient of the first PCB, thesecond PCB and the flexible PCB are equal. In some embodiments, the bendportion is a first bend portion, and the microwave device furtherincludes a third PCB including a third plurality of through-holes, thethird PCB bonded to the flexible PCB and spaced apart from the secondPCB exposing a second bend portion of the flexible PCB, a thirdplurality of electrical components bonded to the flexible PCB withinrespective third plurality of through-holes, and a third cover coveringthe third PCB, where the third PCB is stacked below the first PCB andthe second PCB such that at least a portion of the first PCB is disposedbetween the second PCB and the third PCB.

In some embodiments, an area of the second bend portion is greater thanan area of the first bend portion. In some embodiments, the first PCBincludes a first conductive layer covering sidewalls of the firstplurality of through-holes, and the first conductive layer comprises alayer of conductive material having a mesh structure. In someembodiments, the first plurality of electrical components and the secondplurality of electrical components include microwave components. In someembodiments, the first plurality of electrical components and the secondplurality of electrical components have a thickness between 0.045 inchesand 0.055 inches.

In another aspect, this disclosure describes a method. The methodincludes providing a flexible printed circuit board (PCB). The methodalso includes providing a first PCB having a first plurality ofthrough-holes and a first conductive layer covering sidewalls of thefirst plurality of through-holes. The method further includes providinga second PCB having a second plurality of through-holes and a secondconductive layer covering sidewalls of the second plurality ofthrough-holes. The method further includes bonding the first PCB and thesecond PCB to the flexible PCB, the first PCB spaced apart from thesecond PCB exposing a bend portion of the flexible PCB. The method alsoincludes disposing a first cover on the first plurality ofthrough-holes, disposing a second cover on the second plurality ofthrough-holes, and folding the flexible PCB along the bend portion suchthat the first PCB and the second PCB are stacked.

In some embodiments, the method further includes folding the flexiblePCB such that the first cover faces the second cover. In someembodiments, the method also includes providing the first PCB having acurved portion adjacent to the bend portion of the flexible PCB, thecurved portion having a curvature that conforms to a curvature of thebend portion when the first PCB and the second PCB are stacked. In someembodiments, the method also includes bonding a first plurality ofelectrical components to the flexible PCB within the respective firstplurality of through-holes. In some embodiments, the method furtherincludes providing the flexible PCB with a first ground plane, a secondground plane, and at least one transmission line disposed between thefirst ground plane and the second ground plane, and forming anelectrical contact between a first signal terminal of at least oneelectrical component of the first plurality of electrical components andthe at least one transmission line.

In some embodiments, the method further includes providing the flexiblePCB with at least one microstrip transmission line, a first groundplane, and a dielectric separating the at least one microstriptransmission line and the first ground plane, and forming an electricalcontact between a first signal terminal of the at least one electricalcomponent of the first plurality of electrical components and themicrostrip transmission line. In some embodiments, the method includesforming at least one cavity in a first surface of the first PCB, the atleast one cavity positioned to extend over the at least one microstriptransmission line on the flexible PCB. In some embodiments, the methodfurther includes coating sidewalls of the at least one cavity with theconductive material.

In some embodiments, the method further includes providing the flexiblePCB with a ground plane positioned below the first PCB and the secondPCB, forming an electrical contact between the first cover and theground plane via the first conductive layer covering sidewalls of thefirst plurality of through-holes, and forming an electrical contactbetween the second cover and the ground plane via the second conductivelayer covering sidewalls of the second plurality of through-holes. Insome embodiments, the method further includes disposing a first rigidlayer and a second rigid layer on a side of the flexible PCB that isopposite to a side over which the first PCB and the second PCB arebonded, the first rigid layer and the second rigid layer aligned withthe first PCB and the second PCB respectively.

In another aspect, this disclosure discusses a method. The methodincludes providing a first substrate having at least one groundterminal. The method further includes providing a second substratehaving a first surface and an opposing second surface and having athrough-hole extending between the first surface and the second surface.The method also includes coating sidewalls, and a portion of the firstsurface and a portion of the second surface at rim edges of thethrough-hole with a conductive material. The method also includesbonding the second substrate to the first substrate such that theconductive material on the first surface of the second substrate makeselectrical contact with the at least one ground terminal. The methodfurther includes bonding a microwave component to the first substratewithin the through-hole such that a ground terminal of the microwavecomponent makes electrical contact with the at least one ground terminalof the first substrate. The method also includes bonding a cover to thesecond substrate, the cover at least partially covering the through-holeand making electrical contact with the conductive material covering atleast a portion of the second surface of the second substrate.

In some embodiments, the method further includes bonding the microwavecomponent to the first substrate such that a signal terminal of themicrowave component makes electrical contact with a transmission line inthe first substrate. In some embodiments, the method also includesproviding the first substrate with a first ground plane, a second groundplane, and the transmission line disposed between the first ground planeand the second ground plane. In some embodiments, the method furtherincludes providing the first substrate with at least one microstriptransmission line, and bonding the microwave component to the firstsubstrate such that a signal terminal of the microwave component makeselectrical contact with a the microstrip transmission line. In someembodiments, the method also includes providing the first substrate withat least one microstrip transmission line disposed over a surface of thefirst substrate, and forming at least one cavity in the first surface ofthe substrate, the at least one cavity positioned to extend over the atleast one microstrip transmission line disposed over the surface of thefirst substrate. In some embodiments, the method further includescoating sidewalls of the at least one cavity with the conductivematerial. In some embodiments, the method also includes providing thefirst substrate with the at least one microstrip transmission lineseparated from a ground plane by a dielectric material.

FIG. 1 shows a top view of a first example microwave device 100. Thefirst example microwave device 100 includes a printed circuit board(PCB) 102, a substrate 105, an input switch 106, an output switch 108, afirst filter 110, and a second filter 112. The first example microwavedevice 100 also includes an input interconnect 114 connected to an inputport of the input switch 106, an output interconnect 116 connected to anoutput port of the output switch 108, and additional interconnects 118connecting each end of the first and second filters 110 and 112 to theinput switch 106 or the output switch 108. While not shown in FIG. 1,the first example microwave device 100 also includes a cover (discussedbelow in relation to FIG. 2). The interconnects mentioned above can betransmission lines or paths capable of carrying high-frequency signals,such as radio-frequency (RF) signals and microwave signals. One or moreof the interconnects mentioned above can be implemented using striplinesor waveguides.

The first example microwave device 100 can provide signal processing foran input RF or microwave signal input at the input interconnect 114. Inparticular, the first example microwave device 100 can allow a user toselect one of the first filter 110 and the second filter 112 to filterthe input signal. The input switch 106 can be configured to direct theinput signal to input terminals of either the first filter 110 or thesecond filter 112. Similarly, the output switch 108 can be configured toconnect the output of the selected filter to the output interconnect116. The first example microwave device 100 can also include othermicrowave devices and components such amplifiers, mixers, attenuators,switches, etc. One or more of the microwave devices or components can beimplemented in monolithic microwave integrated circuits (MMICs). Thefirst and second filters 110 and 112 can be thin-film microstrip filtershaving a high dielectric constant (of about 20 to about 26 or about 23),temperature stable, and low loss ceramic. This allows the filters to besmall, high performance, and capable of being surface mounted. The highdielectric constant can provide excellent electro-magnetic fieldconfinement, resulting in a reduction in the size of the microwavedevices for a given operating power. The reduction in size of thedevices, in turn, enables employing low profile microwave devices havinglow thickness (about 0.045 inches to about 0.055 inches or about 0.05inches). Such low profile microwave devices readily lend themselves tothin-film manufacturing processes. The precision, predictability andrepeatability of the thin-film based first and second filters 110 and112 enables a no-tune filter module. In particular, the filter modulesare not based on filters which are assemblies of discrete elements whichare individually tuned due to lack of discrete element precision andassembly variables, resulting in variable and unpredictable filterscattering parameters. These variations in performance can lead tofurther variation and technician tuning at the module level andconsequently high unit cost. The thin-film first and second filters 110and 112 can avoid variations and high cost. Each of the first and secondfilters 110 and 112 can have a length of about 0.35 inches to about 0.45inches or about 0.4 inches, and a width of about 0.095 inches to about0.15 inches, or about 0.1 inches.

FIG. 2 shows a cross-sectional view of the first example microwavedevice 100 along the axis A-A indicated in FIG. 1. FIG. 2 shows thesubstrate 105, the printed circuit board 102, and the second filter 112.The substrate 105 can include one or more stripline interconnectingimpedance controlled transmission lines that are shielded. The substrate105 can be rigid or flexible. To provide low loss and improved impedanceprecision, the substrate 105 can use dielectric materials having lowdielectric constant ε_(r), such as about 1.5 to about 3.5 or about 2.5,and low dielectric loss tangent (tan δ) value of about 0.001 to about0.002 or about 0.0015. The substrate 105 includes a top ground plane122, a bottom ground plane 124, a dielectric layer 140 separating thetop ground plane 122 and the bottom ground plane 124, and a signalinterconnect 118 coupled, through a via, to a contact pad 126 on thesurface of the substrate 105 facing the second filter 112. Specifically,the top ground plane 122 and the contact pad 126 can be formed on orembedded in a top surface 136 of the substrate 105 and the bottom groundplane 124 can be formed on or embedded in a bottom surface 138 of thesubstrate 105. While not shown, a portion, or the entirety, of each ofthe input interconnect 114, the output interconnect 116 and theinterconnects 118 can be formed in the substrate 105.

The second filter 112 includes a ground terminal 128 and a signalterminal 130 disposed on a base of the filter 112. The ground terminal128 makes electrical contact with the top ground plane 122, while thesignal terminal 130 makes electrical contact with the contact pad 126.In one or more embodiments, the ground terminal 128 and the signalterminal 130 can be soldered to the top ground plane 122 and the contactpad 126, respectively.

Referring to FIG. 1, the PCB 102 defines through-holes 120 within whichthe input switch 106, the output switch 108, the first filter 110 andthe second filter 112 are placed. The through-holes extend between a topsurface 192 and a bottom surface 194 of the PCB 102. The PCB 102 can bea dual plated PCB, where both the first side 192 and the second side 194of the PCB 102 are plated with a conducting material, such as copper oraluminum. In some embodiments, certain or limited portions of the sidesof the PCB 102 are plated or covered with the conducting material, forexample, portions at the rim edges 190 of the through-holes 120. Thethrough-holes 120 also define sidewalls 196 in the PCB 102. Thesesidewalls 196 also can be covered with a conducting material such ascopper or aluminum, which can conductively couple to the conductingmaterial plated on the sides of the PCB 102, for example along the rimedges 190 of the through-holes 120. As shown in the example embodimentof FIG. 2, the sidewalls 196 of the PCB 102 within the through-holes120, the top surface 192 of the PCB 102 and the bottom surface 194 ofthe PCB 102 are covered with a conductive material 104. The conductivematerial 104 on the sidewalls 196 of the PCB 102 within thethrough-holes 120 can be of a different composition or thickness thatthat of the conducting material on the top and bottom surfaces 192 and194 of the PCB 102. The conductive material 104 on the sidewalls 196 canenable a conductive path between the conductive material 104 on the topsurface 192 of the PCB 102 and the bottom surface 194 of the PCB 102. Insome implementations, the conductive material 104 may at least partiallycover the sidewalls. In some implementations, the conductive material104 may entirely cover the sidewalls.

The conductive material on the bottom surface of the PCB 102 can makeelectrical contact with the ground plane 122 of the substrate 105, whilethe conductive material on the top surface of the PCB 102 can makeelectrical contact with a cover 132. The cover 132 can include aconductive material such as copper, aluminum, or stainless steel. Insome implementations, the cover 132 can be coated or plated with nickelor gold. The conductive material 104 on the PCB 102 provides electricalcontact between the cover 132 and the ground plane 122 on the substrate105. The ground plane 122 in combination with the conductive material104, and the cover 132 can provide a shielded enclosure for the secondfilter 112. Similar shielded enclosures can also be provided for thefirst filter 110, the input switch 106 and the output switch 108.Shielding the first filter 110 and the second filter 112 allowsmaintaining signal isolation and high fidelity.

In one or more embodiments, the PCB 102 can include an array orconfiguration of the through-holes 120 to accommodate RF and microwavecomponents and devices. Each of the through-holes in the array can havea conductive material, such as the conductive material 104, whichprovides a conductive path between the conductive cover 132 and theground plane 122 of the substrate, thereby forming a shielded cavitywithin the through-hole.

FIG. 3 shows a cross-sectional view of a second example microwave device200. The microwave device 200 shown in FIG. 3 is in many aspects similarto the first example microwave device 100 shown in FIG. 2. To thatextent, similar features are referred to with same reference numerals.Unlike the first example microwave device 100 shown in FIG. 1, whichincludes a signal interconnect 118 that may be a stripline transmissionline, the second microwave device 200 shown in FIG. 3 includes amicrostrip transmission line 134. The microstrip transmission line 134can be formed on the side of the substrate 105 that faces the PCB 102.The microstrip transmission line 134 can be electrically connected tothe contact pad 126, which, in turn, is electrically connected to thesignal terminal 130 of the second filter 112. The microstriptransmission line 134 can be separated from the bottom ground plane 124by the dielectric layer 140. On the surface of the substrate 105, themicrostrip transmission line 134 can be formed on the same plane as thetop ground plane 122 and can be separated from the top ground plane 122by an air gap, the dielectric layer 140 or by some other dielectricmaterial.

The PCB 102 can include a cavity or a tunnel 142 that extends over themicrostrip transmission line 134. The cavity 142 can extend over anentire length of the microstrip transmission line 134. The cavity 142can be formed in the bottom surface 194 of the PCB 102, and can extendlaterally from the sidewall 196 of the through-hole 120. The sidewallsof the cavity 142 can be coated with the conductive material 104. Insome instances, the sidewalls of the cavity 142 can be completelycovered with the conductive material 104. In some instances only aportion of the sidewalls of the cavity 142 can be covered with theconductive material 104. In some instances, the conductive material 104can form a mesh like structure on the sidewalls of the cavity 142. Themesh can include an interlace structure formed from the conductivematerial 104 where the mesh can include regular or irregularly arrangeddiscontinuities in the conductive material 104. In some instances, theconductive material 104 on the sidewalls of the cavities can makeelectrical contact with the ground plane 122 when the PCB 102 ispositioned over the substrate 105. The conductive material 104 canprovide electromagnetic shielding to the microstrip transmission lines134.

FIG. 4 shows a top view of the second example microwave device 200 shownin FIG. 3. The microstrip transmission lines 134 are shown in brokenlines connecting the input switch 106 to the first filter 110 and thesecond filter 112, and the output switch 108 to the first filter 110 andthe second filter 112. In addition FIG. 4 shows an outline of thecavities 142 formed in the PCB 102. A width of the cavity 142 can begreater than a width of the respective microstrip transmission line 134to avoid any electrical contact between the microstrip transmission line134 and the conductive material 104 disposed on the sidewalls of thecavity 142. While not shown in FIG. 4, in some instances, the inputinterconnect 114 and the output interconnect 116 may also be formedusing microstrip transmission lines. In such instances, the PCB 102 caninclude cavities that extend over the input interconnect 114 and theoutput interconnect 116 as well.

FIG. 5 shows a top view of a third example microwave device 200. Thethird example microwave device 300 is shown without top covers, whichare discussed further below. Further, the third example microwave device300 is shown in an un-folded configuration. A folded configuration ofthe third example microwave device 300 is discussed below in relation toFIG. 8. The third example microwave device 300 includes a bottom PCB 102and a top PCB 152 both of which are disposed on a substrate 204. Thethird example microwave device 300 is similar to the first examplemicrowave device 100 discussed above in relation to FIG. 1 in manyrespects, and to the extent that the third example microwave device 300and the first example microwave device 100 have common elements, suchcommon elements are referred to with the same reference numerals. Thebottom PCB 102 is similar to the PCB 102 shown in FIG. 1, in that likethe PCB 102 of the first example microwave device 100, the bottom PCB102 of the third example microwave device 300 also includesthrough-holes 120 that can accommodate the input switch 106, the outputswitch 108, the first filter 110, and the second filter 112. Inaddition, the top PCB 152 can include through-holes 120 that accommodatea third filter 154 and a fourth filter 156. The third filter 154 and thefourth filter 156 can be similar to the first and second filers 110 and112. Furthermore, the third example microwave device 300 includes signalinterconnects 118 that connect the input switch 106 and the outputswitch to the third filter 154 and the fourth filter 156.

The operation of the third example microwave device 300 is similar tothe operation of the first example microwave device 100, in that theinput switch 106 and the output switch 108 can be individuallyconfigured to select one of the four filters in the signal path of theinput signal received at the input interconnect 114. While not shown inFIG. 2, the third example microwave device 300 also includes additionalcontrol terminals that can receive control signals for the configurationof the input switch 106 and the output switch 108.

The bottom PCB 102 and the top PCB 152 are disposed on a substrate 204.The substrate 204, as discussed further below, can include a flexiblePCB layer 206 including stripline transmission lines or microstriptransmission lines, similar to those discussed above in relation to thesubstrate 105 shown in FIGS. 2 and 3.

FIG. 6 shows a top view of a fourth example microwave device 400including microstrip transmission lines. The microwave device 400 shownin FIG. 6 is similar to the microwave device 300 shown in FIG. 5, exceptthat in the fourth example microwave device 400 shown in FIG. 6,microstrip transmission lines 134 are used to implement the signalinterconnects 118. As discussed above in relation to FIGS. 3 and 4, thePCB 102 can include cavities 142 that extend over the microstriptransmission lines 134. The microwave device 400 shown in FIG. 6 alsoincludes cavities 142 formed in the top PCB 152 and the bottom PCB 102that extend over the microstrip transmission lines 134. The cavities 142can have the conductive material 104 disposed over at least a portion ofthe sidewalls of the cavities 142. The microstrip transmission lines 134can be formed on the surface of the substrate 204, in a manner similarto that discussed above in relation to substrate 105 shown in FIGS. 3and 4.

FIGS. 7A and 7B show a side view of the third example microwave device300 shown in FIG. 5, and an expanded view of the bottom PCB 102. FIGS.7A and 7B also represent a side view of the fourth example microwavedevice 400 shown in FIG. 6. The substrate 204 can include a bottom rigidlayer 208 disposed on the side of the flexible PCB layer 206 that facesaway from the bottom PCB 102 and a top rigid layer 210 on the side ofthe flexible PCB layer 206 that faces away from the top PCB 152. The topand bottom rigid layers 210 and 208 do not cover the entire surface ofthe flexible PCB layer 206. For example, a bend portion 212 of theflexible PCB layer 206 is devoid of the top and bottom rigid layers 210and 208. Further, a bottom cover 132 covers the bottom PCB 102 and a topcover 228 covers the top PCB 152. The bottom cover 132 and the top cover228 can be similar to the cover 132 discussed above in relation to FIG.2. A portion of the bottom PCB 102 adjacent to the bend portion 212 caninclude a bottom curved surface 218. Similarly, a portion of the top PCB152 adjacent to the bend portion 212 can include a top curved surface220. The top and bottom rigid layers 208 and 210 can not only providerigidity to the microwave device, but also can provide connectivity toexternal devices. For example, the top and bottom rigid layers 208 and210 can include printed circuit boards with contact pads andinterconnects that can allow the microwave device 200 to be connected toother circuitry or be mounted on other devices or printed circuitboards. In some implementations, the top and bottom rigid layers 208 and210 can be made of the same material as the top and bottom PCBs 102 and152. In some implementations, the top and bottom rigid layers 208 caninclude contact pads for input and output terminals, which can be usedto solder surface mount the microwave device 200 on other PCBs anddevices.

With regards to the example dimensions, third example microwave device300 and the fourth example microwave device 400 can have a thickness Tof about 0.04 to about 0.07 or about 0.057 inches. Each of the bottomPCB 102 and the top PCB 152 can have a thickness T_(pcb) of about 0.03to about 0.05, or about 0.04 inches. The flexible PCB layer 206 can havea thickness of about 0.0040 to about 0.012 or about 0.0080 inches. Therigid layer 208 can have a thickness T_(rigid) of about 0.0040 to about0.012 or about 0.0080 inches. The cover 132 can have a thicknessT_(cover) of about 0.0020 to about 0.0080 or about 0.0050 inches.Referring to FIGS. 5 and 6, the third example microwave device 300 andthe fourth microwave device 400 can have a length L of about 1.3 toabout 0.7 or about 1 inch, and an unfolded width W of about 0.6 to about1.1 or about 0.88 inches. The width W_(top-pcb) of the top PCB 152 canbe about 0.2 to about 0.6 or about 0.4 inches. The width W_(bot-pcb) ofthe bottom PCB 102 can be about 0.2 to about 0.6 or about 0.4 inches. Insome implementations, the top and bottom PCBs can have thicknessesT_(pcb) that is at least twice a thickness of an electrical componentplaced within the shielding cavity.

FIG. 8 shows a cross-sectional view of the third example microwavedevice 300 in a folded configuration along axis B-B shown in FIG. 5.FIG. 8 also represents a cross-sectional view of the fourth examplemicrowave device 400 in a folded configuration along the axis B-B shownin FIG. 6. The third example microwave device 300 is folded along thebend portion of the flexible PCB layer 206, such that the top PCB 152 ispositioned on top of the bottom PCB 102. Specifically, the top cover 228and the bottom cover 132 can face each other. The flexible PCB layer 206bends around one end of the folded third example microwave device 300 toconnect the bottom PCB 102 to the top PCB 152. The bottom PCB 102defines through-holes 120 that accommodate the first filter 110 and thesecond filter 112. Similarly, the top PCB 152 defines through-holes 120that accommodate the third filter 154 and the fourth filter 156. Thebottom curved surface 218 of the bottom PCB 102 can have a radius thatis substantially equal to a bend radius of the bend portion 212 of theflexible PCB layer 206. Similarly, the top curved surface 220 of the topPCB 152 also can have a radius that is substantially equal to the bendradius of the bend portion 212. In some implementations, the top curvedsurface 220 and the bottom curved surface 218 can have a curvature thatconforms to the curvature of the bend portion 212. In someimplementations, the top curved surface 220 and the bottom curvedsurface 218 abut the bend portion 212, thereby providing support to thebend portion 212 of the flexible PCB layer 206 and reducing the risk ofbreakage of the flexible PCB layer 206. In some implementations, anadhesive material may also be disposed between the each of the bottomcurved surface 218 and the top curved surface 220 and the bend portion212 of the flexible PCB layer 206. In some implementations, an adhesivematerial 250 can be disposed between the bottom cover 132 and the topcover 228 to adhere the two covers together. In some implementations,the adhesive material 250 can include a conductive material.

FIG. 9 shows an expanded view of a portion A of the third examplemicrowave device 300 shown in FIGS. 5 and 8. In particular, FIG. 6 showsthe first filter 110 and the bottom PCB 102 disposed on a multilayeredflexible PCB layer 206. The flexible PCB layer 206 includes a firstdielectric layer 252, a second dielectric layer 254, and a thirddielectric layer 256. On or more of these layers may be optional and canbe absent, in certain implementations. A top conductive layer or a topground plane 258 can be formed over the first dielectric layer 252. Theground plane 258 can extend substantially over the entire surface of theflexible PCB layer 206, except where apertures in the ground pane 258are formed within which signal contact pads 264 are formed in electricisolation from the ground plane 258. The top ground plane 258 iselectrically connected to the ground terminal 262 of the first filter110. The signal contact pad 264, in turn, makes electrical contact witha signal terminal 276 of the first filter 110. The top ground plane 258also makes contact with a conductive material 266 coated on the bottomPCB 102. The conductive material 266 is deposited on all the wallsurfaces of the through-hole 120 formed in the bottom PCB 102. Theconductive material 266 also covers at least a portion of both planarsurfaces of the bottom PCB 102. In some implementations, a conductiveadhesive or a solder 260 can be used to electrically connect the topground plane 258 to the ground terminal 262 and to the conductivematerial 266 of the bottom PCB 102. The conductive adhesive or thesolder 260 also can be used to electrically connect the signal contactpad 264 to the signal terminal 276 of the first filter 110.

The flexible PCB layer 206 can include a stripline 274 interconnectingimpedance controlled transmission line disposed between the firstdielectric layer 252 and the second dialectic layer 254. The stripline274 can be connected to the signal contact pad 264 through vias formedin the first dielectric layer 252. The flexible PCB layer 206 canfurther include a bottom ground plane 272 that substantially covers theentire bottom surface of the flexible PCB layer 206. The top groundplane 258 and the bottom ground plane 272 can be electrically connectedthrough vias and intermediate conductive layers 268. The top groundplane 258 and the bottom ground plane 272 help shield the stripline 274from signal interference.

In one or more implementations, the first dielectric layer 252, thesecond dielectric layer 254, and the third dielectric layer 256 areformed using dielectric materials having low dielectric constant ε_(r),of about 1.5 to about 3.5 or about 2.5, and low dielectric loss tangent(tan δ) value of about 0.001 to about 0.002 or about 0.0015. Having lowvalue dielectric constant and low dielectric loss can allow the first,second, and third dielectric layers 252, 254, and 256 to have arelatively small thickness. Smaller thickness of these layers can reducethe overall thickness of the flexible PCB layer 206, which allows for asmaller bending radius of the flexible PCB layer 206. Having a smallbending radius can allow building the third example microwave device 300at even smaller thicknesses and profiles. In some implementations,example thicknesses of the first and second dielectric layers 252 and254 can be about 0.002 to about 0.005 or about 0.003 inches. In someimplementations, the thickness of the third dielectric layer 256 can beabout 0.002 to about 0.005, or about 0.001 to about 0.003 or about 0.002inches. As an example, the first, second and third dielectric layers252, 254, and 256 can include pyralux TK materials manufactured byDUPONT®, however, other dielectric materials satisfying the abovementioned dielectric constant and dielectric loss values can be used. Insome implementations, the bending radius of the flexible PCB layer 206can be about 0.040 to about 0.070 inches. The stripline 274 can have acharacteristic impedance of about 50 ohms and an RF insertion loss perinch of approximately 0.7 dB at 20 GHz.

The bottom cover 132 (shown in FIG. 5) makes electrical contact with theconductive layer 266 (shown in FIG. 6) of the bottom PCB 102 therebymaking an electrical contact with the top ground plane 258. In thismanner, the bottom cover 132, the conductive material 266 on thesidewalls of the bottom PCB 102, and the top ground plane 258 togethercan form a shielded cavity or enclosure for the first filter 110.Similarly, the top ground plane 258 and the bottom ground plane 272 canprovide shielding to the stripline 274. The stripline 274 can representthe transmission lines 118 that carry the signal to and from the firstfilter 110. In some implementations, the stripline 274 can extend fromunder the bottom PCB 102 through the bend portion 212 to under one ormore components on the top PCB 152. For example, the stripline 274 canbe used to implement the interconnects 118 (FIG. 3) between the thirdand fourth filters 154 and 156 and the input and the output switches 106and 108.

In some implementations, the bottom PCB 102 and the top PCB 152 can havea thermal coefficient of expansion that is substantially similar to thatof the flexible PCB layer 206. This reduces the risk of detachment ofthe flexible PCB layer 206. In some implementations, the vias in theflexible PCB layer 206 can be formed using laser, and can have diametersof about 0.003 to about 0.005 or about 0.004 inches.

FIG. 10 shows an expanded view of a portion A of the fourth examplemicrowave device 400 shown in FIGS. 6 and 8. The cross-sectional viewshown in FIG. 10 is similar to the cross-sectional view of the thirdexample microwave device 300 shown in FIG. 9. To that extent, commonfeatures are referred to with the same reference numerals. Thecross-sectional view shown in FIG. 10 shows a microstrip transmissionline 280 disposed on the flexible PCB layer 206. The microstriptransmission line 280 is electrically coupled to the contact pad 264,which, in turn, is electrically connected to the signal terminal 276 ofthe first filter 110. The microstrip transmission line 280 can be usedto implement the microstrip transmission line 134 shown in the top viewof the fourth example microwave device 400. FIG. 10 also shows a cavityor tunnel 282 defined by the bottom PCB 102 and the flexible PCB layer206. The cavity 282 can be similar to the cavity 142 discussed above inrelation to FIG. 3, and can include sidewalls that are at leastpartially coated with the conductive material 266 to provide shieldingto the microstrip transmission line 280.

FIGS. 11 and 12 show block diagrams of an unfolded and a folded,respectively, microwave device 280 including three stackable PCBs.Referring again to FIG. 8, in some implementations, the third examplemicrowave device 300 and the fourth example microwave device 400 caninclude one or more PCBs in addition to the bottom PCB 102 and the topPCB 152. For example, as shown in FIG. 11, the microwave device 280 caninclude a third PCB 282, positioned on the flexible PCB layer 206 spacedapart from the top PCB 152. The third PCB 282 can be similar to thebottom PCB 102 and the top PCB 152 discussed above. As shown in FIG. 12,the third PCB 282 can be stacked under the bottom PCB 102. The flexiblePCB layer 206, which in FIG. 8 terminates under the top PCB 152, caninstead form an additional bend region 284, which can extend out to theleft, bend downwards, and connect to the third PCB 282 stacked under thebottom PCB 102. In some such arrangements, the additional bend portion284 can have an area that is greater than the area of the bend portion212. The larger area of the additional bend portion 284 allows theadditional bend portion to traverse a larger distance to allow the thirdPCB 282 to be stacked under the bottom PCB 102. The third PCB 282includes a third cover 286, that in the position shown in FIG. 12, isfacing the bottom PCB 105, and top rigid layer of the third PCB 282faces the bottom rigid layer 208 of the bottom PCB 102. In anotherexample arrangement, the third PCB 282 can be positioned spaced apartfrom the bottom PCB 102, instead of being positioned spaced apart fromthe top PCB 152, as shown in FIG. 11, such that the additional bendportion extends between the bottom PCB 102 and the third PCB 282. Insuch arrangements, the third PCB can be stacked below the bottom PCB 102such that the cover 286 can face away from the bottom PCB 102. In suchan arrangement, the three PCBs along with the flexible PCB layer 206 canapproximately form a “Z” shape. In such manner, multiple PCBs can bestacked, where each PCB is connected to another PCB in the stack throughthe flexible PCB layer. The stacking of the PCBs allows including alarge number of microwave components within the same footprint, therebyincreasing device density.

FIG. 13 shows a flow diagram for a process 500 of manufacturing amicrowave device. The process includes providing a flexible printedcircuit board including at least one ground plane and at least onetransmission line (stage 502). One example of this process stage hasbeen discussed above in relation to FIGS. 5-12 where the flexible PCBlayer 206 includes a top ground plane 258, a bottom ground plane 272 anda stripline 274 transmission line or a microstrip transmission line 280.As discussed above, the flexible PCB layer 206 can be formed usingmultiple layers of dielectric material having low dielectric constantand low dielectric loss. Stripline transmission lines 274 can beincluded between any two of the dielectric layers. Microstriptransmission lines 280 can be formed on top of the first dielectriclayer 252 using patterning techniques. The flexible PCB layer 206 canalso include contact pads for making electrical contact with circuitcomponents mounted thereon, as well as laser formed vias that connectthe contact pads to underlying striplines or to other ground planes. Inone example, the flexible PCB layer 206 can be provided with a thicknessof about 0.006 to about 0.01 inches and have a bending radius of about0.040 to about 0.070 inches.

The process 500 further includes providing a first PCB having a firstplurality of through-holes and a first conductive layer coveringsidewalls of the first plurality of through-holes (stage 504). Oneexample of this method stage has been discussed above in relation toFIGS. 5-12, where the bottom PCB 102 includes a plurality ofthrough-holes 120. The bottom PCB 102 can be a double cladded PCB, whichincludes a metal coating both the top and bottom surfaces of the PCB.Each of the plurality of through-holes 120 can be formed usingphotolithography techniques, chemical etching, machining (e.g., routingor milling), or a laser cutting process. The sidewalls of each of thethrough-holes 120 can be chemically activated, and coated with aconductive material such as copper or aluminum. In some implementations,the sidewalls of the through-holes 120 can be coated with the conductivematerial using PCB processes for forming metallized vias in the PCB.

The process 500 additionally includes providing a second PCB having asecond plurality of through-holes and a second conductive layer coveringsidewalls of the second plurality of through-holes (stage 506). Oneexample of this process stage has been discussed above in relation toFIGS. 5-12. For example, as shown in FIGS. 5-10, the top PCB 152 isprovided with a plurality of through-holes 120. The second PCB can beformed in a manner similar to that discussed above in relation to thefirst PCB.

In some instances, where microstrip transmission lines are used (such asthe microstrip transmission lines 134 and 280 shown in FIGS. 6 and 10)cavities can be formed in both the first PCB and the second PCB thathave a pattern such that when the first and the second PCB are bonded tothe flexible PCB, the cavities extend over the microstrip transmissionlines. In some examples, the cavities 142 can be formed in the bottomsurface 194 of the PCB 102 using photolithography techniques, chemicaletching, machining (e.g., routing or milling), or a laser cuttingprocess. As an example, the cavities 142 can be formed on the bottomsurface 194 of the PCB 102 such that they extend laterally form thesidewall 196. In some instances, widths of the cavities 142 can beselected to be greater than the width of the microstrip transmissionlines 134. In addition, at least a portion of the sidewalls of cavitiescan be coated with the conductive material to provide shielding to themicrostrip transmission lines. The conductive material can be depositedon the walls of the cavities using metal deposition techniques such aselectroplating, sputtering, evaporation, and the like.

The process 500 also includes bonding the first PCB and the second PCBto the flexible PCB (stage 508). One example of this process stage hasbeen discussed above in relation to FIGS. 5-12, where the bottom PCB 102and the top PCB 152 are bonded onto the flexible PCB layer 206. Thebottom PCB 102 and the top PCB 152 are spaced apart to expose a bendportion 212 of the flexible PCB layer 206. In some implementations, asolder reflow process can be used to physically and electrically bondthe conductive surfaces of the bottom PCB 102 and the top PCB 152 to theground plane contact pads on the flexible PCB layer 206. In some otherimplementations, a conductive adhesive can be used to physically andelectrically bond the bottom PCB 102 and the top PCB 152 to the flexiblePCB layer 206.

The process 500 further includes disposing a first cover on the firstplurality of through-holes (510) and disposing a second cover on thesecond plurality of through-holes (512). At least one example of theseprocess stages has been discussed above in relation to FIGS. 5-12. Forexample, FIGS. 7A, 7B and 8 show a bottom cover 132 disposed over thethrough-holes 120 in the bottom PCB 102 and a top cover 228 disposedover the through-holes 120 in the top PCB 152. In some instances, thebottom cover 132 and the top cover 228 completely cover the respectivethrough-holes. In some examples, the bottom cover 132 and the top cover228 can only partially cover the respective through-holes. In someinstances the bottom cover 132 and the top cover 228 can be bonded tothe respective PCB such that the covers make electrical contact with theconductive material 266 that is deposited over the sidewalls of thethrough-holes and over a portion of the top and bottom surfaces aroundthe rim edges 190 of the though holes 120. The covers can be bonded totheir respective PCBs using solder or a conductive adhesive.

The process 500 also includes folding the flexible PCB layer along thebend portion such that the first PCB and the second PCB are stacked(stage 514). As shown in FIG. 8, the flexible PCB layer 206 is folded orbent at the bend portion 212 such that the top PCB 152 is stacked overthe bottom PCB 102. The PCBs are stacked, which can reduce a footprintof the microwave device. Also as shown in FIG. 12 a third PCB 282 can bestacked below the bottom PCB 102 and can include another bend portion284, which can be folded to stack the third PCB 282 below the bottom PCB102.

In some instances, the process 500 can further include placing circuitcomponents within the through-holes on the flexible PCB layer. Oneexample of this process has been discussed above in relation to FIGS.6-10. For example, the circuit components such as the input switch 106,the output switch 108, and the plurality of filters 110, 112, 154, and156 are placed on the flexible PCB layer 206 within their respectivethrough-holes 120. The circuit components can be bonded to the flexiblePCB layer 206 using a soldering process or by using a conductiveadhesive. The components can be placed such that the ground terminal andsignal terminal of each circuit component is in proper electricalcontact with the corresponding contact pads on the flexible PCB layer206.

In some implementations, the circuit components may be placed on theflexible PCB layer 206 prior to the bonding of the top and bottom PCBs152 and 102 to the flexible PCB layer 206. This may provide a benefit ofhaving easy access to the circuit components while they are bonded tothe flexible PCB layer 206.

In some implementations, the process can further include singulation ofindividual microwave devices from a panel of multiple microwave devicesformed as a panel. For example, the flexible PCB 206 can be formed withinterconnects, ground planes, and contact pads associated with multiplemicrowave devices. The flexible PCB 206 can include multiple portions,for example, arranged in rows and columns, where each portion includesinterconnects ground planes and contact pads associated with onemicrowave device. Similarly, a panel PCB can have multiple portionsassociated with multiple microwave devices, and positioned to align withcorresponding portions on the flexible PCB 206. For example, eachportion of the panel PCB representing a single microwave device, caninclude sub-portions that correspond to the bottom PCB 102 and the topPCB 152. The panel PCB can also include cut-outs positioned between thesub-portions that expose the bend portion 212 of the flexible PCB 206when the panel PCB is bonded to the flexible PCB 206. The sub-portionsthat correspond to the bottom PCB 102 and top PCB 152 can includethrough-holes 120 with conductive material 104 disposed at least ontheir sidewalls. The panel PCB can be patterned using typical PCBformation processes such as photolithography, chemical etching, lasercutting and machining.

Similarly, a cover material having multiple portions corresponding tomultiple microwave devices can be bonded to the panel PCB. Each portionof the cover that corresponds to a microwave device can includesub-portions corresponding to the top cover 228 and the bottom cover132. The cover may also include cut-outs that correspond to the cut-outson the panel PCB that can expose the bend portion 212 on the flexiblePCB 206. Individual microwave devices can be singulated by cutting thepanel PCB, the flexible PCB 206 and the cover.

The electrical components associated with each of the microwave devicesdefined by the flexible PCB 206 and the panel PCB can be disposed on theflexible PCB 206 before or after the bonding of the panel PCB on theflexible PCB 206. Further, the electrical components can be bonded tothe flexible PCB 206 before or after singulation.

In some implementations, the process can further include bonding the toprigid layer 210 and the bottom rigid layer 208 to the flexible PCB layer206. In some implementations, a PCB material can be bonded to theflexible PCB layer 206 and then patterned using patterning techniquessuch as photolithography, chemical etching, machining, and laser cuttingto cut out the PCB layer near the bend portion 212 to form the top rigidlayer 210 and the bottom rigid layer 208. In some instances, theflexible PCB 206 can be formed with a rigid layer that includes portionsthat correspond to multiple microwave devices, where each portioninclude sub-portions corresponding to the top rigid layer 210 and thebottom rigid layer 208. The rigid layer can be bonded to the flexiblePCB on a surface that is opposite to the surface on which the PCB panelis bonded. During singulation, the rigid layer is can be cutsimultaneously with the panel PCB, the flexible PCB 206 and the cover toform the top rigid layer 210 and the bottom rigid layer 208 of eachmicrowave device. The singulated microwave devices can then beindividually folded along their respective bend portion 212 to formindividual stacked microwaved devices.

In some implementations, the first PCB 102 and the second PCB 152 can bereplaced with metal boards. In some such implementations, the metalboards can have through-holes 120, but may not include the conductivecoating 104, as the metal board itself would provide a conductive pathbetween the covers and the ground plane of the substrate 105 or theflexible PCB layer 206.

FIG. 14 shows a flow diagram of another process 600 of manufacturing amicrowave device. The process 600 includes providing a first substratehaving at least one ground terminal (602). At least one example of thisprocess stage has been discussed above in relation to FIGS. 1-10. Forexample, FIGS. 1-4 show a substrate 105 having a ground terminal 128.The substrate can include a top ground plane 122, a bottom ground plane124, and a dielectric layer 140 positioned there between. The substrate105 can be formed using any metal deposition technique that can be usedto deposit and pattern metal layers on both opposing surfaces of thesubstrate 105. The patterning can form contact pads 126 and the groundterminals 128 for connection to electrical components. In someinstances, the patterning process can also pattern microstriptransmission lines 134 connecting contact pads or ground terminalsformed on the substrate 105. The substrate 105 can also includestripline transmission lines 118 that are positioned such that at leasta portion of the stripline transmission lines 118 is covered by thedielectric material 140.

The process 600 further includes providing a second substrate having afirst surface and an opposing second surface and having a through-holeextending between the first surface and the second surface (604). Atleast one example of this process stage has been discussed above inrelation to FIGS. 1-10. For example, as shown in FIGS. 2 and 3, the PCB102 includes through-holes 120 extending between a first surface (thetop surface 192) and a second surface (the bottom surface 194) of thePCB 102. The through-holes can be formed using photolithographytechniques, chemical etching, machining (e.g., routing or milling), or alaser cutting process.

The process 600 further includes coating sidewalls and a portion of thefirst surface and a portion of the second surface at rim edges of thethrough-holes with a conductive material (606). At least one example ofthis process stage has been discussed above in relation to FIGS. 1-10.For example, as shown in FIGS. 2 and 3, a conductive material 104 can bedeposited over the sidewalls 196 and at least a portion of the topsurface 192 and the bottom surface 194 near the rim edges 190 of the PCB102. In some examples, the sidewalls 196 of each of the through-holes120 and the top and bottom surfaces 192 and 194 of the PCB 102 can bechemically activated and coated with a conductive material 104 such ascopper or aluminum. In some implementations, the sidewalls 196 of thethrough-holes 120 and portions of the top and bottom surface 192 and 194can be coated with the conductive material 104 using PCB processes forforming metallized vias in the PCB.

The process 600 also includes bonding the second substrate to the firstsubstrate such that the conductive material on the first surface of thesecond substrate makes electrical contact with the at least one groundterminal (608). At least one example of this process stage has beendiscussed above in relation to FIGS. 1-10. For example, FIGS. 2 and 3show the PCB 102 bonded to the substrate 105, such that the conductivematerial 104 on the PCB 102 makes electrical contact with the groundplane or terminal 122. In some examples, a solder reflow process can beused to physically and electrically bond the conductive surfaces of thePCB 102 to the ground plane or terminal 122 of the substrate 105. Insome examples, a conductive adhesive also can be used.

The process 600 also includes bonding a microwave component to the firstsubstrate within the through-hole such that a ground terminal of themicrowave component makes electrical contact with the at least oneground terminal of the first substrate (610). At least one example ofthis process stage has been discussed above in relation to FIGS. 1-10.For example, FIGS. 1-5 show circuit components such as the input switch106, the output switch 108, and the plurality of filters 110 and 112placed on the substrate 105 within their respective through-holes 120.The circuit components can be bonded to the flexible PCB layer 206 usinga soldering process or by using a conductive adhesive. The componentscan be placed such that the ground terminal and signal terminal of eachcircuit component is in proper electrical contact with the correspondingcontact pads on the substrate 105. In some examples, the circuitcomponents may be placed on the substrate 105 prior to the bonding ofthe PCB 102 to the substrate 105. This may provide a benefit of havingeasy access to the circuit components while they are bonded to thesubstrate 105.

The process 600 also includes bonding a cover to the second substrate,the cover at least partially covering the through-hole and makingelectrical contact with the conductive material covering at least aportion of the second surface of the second substrate (612). At leastone example of this process stage has been discussed above in relationto FIGS. 1-10. For example, FIGS. 2 and 3 show a cover 132 bonded to thetop surface 192 of the PCB 102. The cover 132 makes electrical contactwith the conductive material 104 covering at least a portion of the topsurface 192 of the PCB 102. The cover 132 completely covers thethrough-hole 120. However, in some examples, the cover 132 may partiallycover the through-hole 120. The cover 132, the conductive material 104on the sidewalls 196, and the ground plane or terminal 122 provideshielding to the electrical component 112, thereby improving theperformance of the electrical component 112.

In some instances, the process 600 can further include singulation toform individual devices. For example, the substrate 105 can includemultiple portions corresponding to multiple devices, where each portioncan include ground planes, interconnects, and contact pads associatedwith each device. The PCB 102 can be a panel PCB and can includemultiple portions that correspond to multiple devices, where eachportion can include through-holes 120 with at least conductivesidewalls. The panel PCB can be bonded to the substrate 105 such thatindividual device portions on the panel PCB align with correspondingdevice portions on the substrate 105. A cover that also includesmultiple regions corresponding to multiple devices, and can be bonded tothe panel PCB. Individual devices can be singulated by cutting thecover, the PCB, and the substrate 105 appropriately between portionsthat correspond to individual devices.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures areillustrative, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of plural and/or singular terms herein, thosehaving skill in the art can translate from the plural to the singularand/or from the singular to the plural as is appropriate to the contextand/or application. The various singular/plural permutations may beexpressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.).

It will be further understood by those within the art that if a specificnumber of an introduced claim recitation is intended, such an intentwill be explicitly recited in the claim, and in the absence of suchrecitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations).

Furthermore, in those instances where a convention analogous to “atleast one of A, B, and C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, and C”would include but not be limited to systems that have A alone, B alone,C alone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). In those instances where a conventionanalogous to “at least one of A, B, or C, etc.” is used, in general sucha construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, or C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.” Further, unlessotherwise noted, the use of the words “approximate,” “about,” “around,”“substantially,” etc., mean plus or minus ten percent.

The foregoing description of illustrative embodiments has been presentedfor purposes of illustration and of description. It is not intended tobe exhaustive or limiting with respect to the precise form disclosed,and modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the disclosed embodiments.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. A microwave device, comprising: a flexibleprinted circuit board (PCB); a first PCB including a first plurality ofthrough-holes, the first PCB bonded to the flexible PCB; a firstplurality of electrical components bonded to the flexible PCB withinrespective first plurality of through-holes; a first cover at leastpartially covering the first PCB; a second PCB including a secondplurality of through-holes, the second PCB bonded to the flexible PCBand spaced apart from the first PCB exposing a bend portion of theflexible PCB, the second PCB including a second conductive layercovering sidewalls of the second plurality of through-holes; a secondplurality of electrical components bonded to the flexible PCB withinrespective second plurality of through-holes; and a second cover atleast partially covering the second PCB and making electrical contactwith the second conductive layer, wherein the second PCB is stacked onthe first PCB such that the first cover faces the second cover.
 2. Themicrowave device of claim 1, further comprising a first rigid layerdisposed on a side of the flexible PCB opposing to a side on which thefirst PCB is disposed.
 3. The microwave device of claim 1, wherein thefirst cover and the second cover comprise stainless steel.
 4. Themicrowave device of claim 1, further comprising an adhesive layerdisposed between the first cover and the second cover.
 5. The microwavedevice of claim 1, wherein the first PCB includes a first curved portionadjacent to the bend portion of the flexible PCB, and the second PCBincludes a second curved portion adjacent to the bend portion of theflexible PCB.
 6. The microwave device of claim 5, wherein the firstcurved portion and the second curved portion conform to a curvature ofthe bend portion of the flexible PCB.
 7. The microwave device of claim5, further comprising an adhesive layer disposed between the firstcurved portion of the first PCB and the bend portion of the flexiblePCB.
 8. The microwave device of claim 1, wherein the flexible PCBcomprises: at least one signal terminal coupled to at least oneelectrical component from the first plurality of electrical componentsand the second plurality of electrical components, at least onetransmission line coupled to the at least one signal terminal, and adielectric material covering at least a portion of the at least onetransmission line.
 9. The microwave device of claim 8, wherein theflexible PCB has at least one ground plane, the at least one groundplane including a first ground plane and a second ground plane, andwherein the at least one transmission line is disposed between the firstground plane and the second ground plane.
 10. The microwave device ofclaim 1, wherein the flexible PCB comprises: at least one signalterminal coupled to at least one electrical component from the firstplurality of electrical components and the second plurality ofelectrical components, at least one microstrip transmission line coupledto the at least one signal terminal.
 11. The microwave device of claim10, wherein the first PCB includes at least one cavity extending over atleast a portion of a respective at least one microstrip transmissionline, and includes a first conductive layer covering sidewalls of thefirst plurality of through-holes, wherein the first conductive layercovers at least a portion of sidewalls of the at least one cavity. 12.The microwave device of claim 10, wherein the flexible PCB has at leastone ground plane, and the first PCB includes a dielectric layerseparating the at least one microstrip transmission line from the atleast one ground plane.
 13. The microwave device of claim 12, whereinthe dielectric layer has a dielectric constant between 1.5 and 3.5. 14.The microwave device of claim 12, wherein the dielectric layer has adielectric loss tangent value between 0.001 and 0.002.
 15. The microwavedevice of claim 1, wherein a thermal expansion coefficient of the firstPCB, the second PCB and the flexible PCB are equal.
 16. The microwavedevice of claim 1, wherein the bend portion is a first bend portion, themicrowave device further comprising: a third PCB including a thirdplurality of through-holes, the third PCB bonded to the flexible PCB andspaced apart from the second PCB exposing a second bend portion of theflexible PCB; a third plurality of electrical components bonded to theflexible PCB within respective third plurality of through-holes; and athird cover at least partially covering the third PCB, wherein the thirdPCB is stacked below the first PCB and the second PCB such that at leasta portion of the first PCB is disposed between the second PCB and thethird PCB.
 17. The microwave device of claim 16, wherein an area of thesecond bend portion is greater than an area of the first bend portion.18. The microwave device of claim 1, wherein the first PCB includes afirst conductive layer covering sidewalls of the first plurality ofthrough-holes, and the first conductive layer comprises a layer ofconductive material having a mesh structure.
 19. The microwave device ofclaim 1, wherein the first plurality of electrical components and thesecond plurality of electrical components include microwave components.20. The microwave device of claim 1, wherein the first plurality ofelectrical components and the second plurality of electrical componentshave a thickness between 0.045 inches and 0.055 inches.